Throw an exception when Router::generate() is called

Problem/Motivation

In an effort to reduce the number of ways to generate a link, we deprecated calling Router::generate() in Drupal 8.3.0

Last time we tried to remove it, we realised we couldn't because it was on RouterInterface, so we said it will start throwing an exception in Drupal 10.

  /**
   * {@inheritdoc}
   */
  public function generate($name, $parameters = [], $referenceType = self::ABSOLUTE_PATH): string {
    @trigger_error(__METHOD__ . '() is deprecated in drupal:8.3.0 and will throw an exception from drupal:10.0.0. Use the \Drupal\Core\Url object instead. See https://www.drupal.org/node/2820197', E_USER_DEPRECATED);
    return $this->urlGenerator->generate($name, $parameters, $referenceType);
  }

I think we need to remove the @inheritdoc, add a @throws, and then have an exception message which tells people to use the Url object instead.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet